Getting ready to put head back on '94 3.8 and head bolt holes are a bit gunked up. I've seen lots of references to using a thread chaser to clean out the head bolt holes, but I can't seem to find any information on where to get thread chasers what size is needed for my '94 3.8. I suppose it would also be a good idea to do the same for the manifold bolt holes as well. Any pointers on where to get them and what the sizes are that wre needed would be appreicated.

Hmm I've never heard about thread chasers, but i generally use taps to clean out bolt holes. If you do much mechanical work, you ought to buy a set of them at Sears or your favorite tool store. (which means i don't know the size you need lol) The tap won't remove the gunk but it will loosen it so that it can be blown out with an air compressor.

Before you choose a set of taps though, do use a thread gauge on your bolts to determine the threads per inch.

Aha! The Factory Service Manual for my 93 sez to cleen teh threads with a "7/16-14 tap". Weird. That sounds like an inch size....what are standard (inch) bolts doing in a 3800?

There are a number of SAE thread bolts on the motor, mostly in the block (carry over from the days before metric motors were introduced with the 60degree V6)

Yeah I noticed that. The plenum bolts are 8mm. The lower intake manifold was 3/8 standard. I was walking back and forth to the toolbox scratching my head to figure out what was going on. Usually, I just take 10,13, and 15 to the hood and thats just about all I need.

With these motors, you are going to need a set of metric and SAE taps (perhaps even a couple of NPT taps too.) For instance, the oil pan bolts are 1/4"-20, yet as you discovered, the top of the motor is mostly metric

The route GM took towards "metric-izing" the existing motors was to leave the blocks alone and do the accessory drives, fuel system, and other optional parts first. (Where they become part of a common "pool" of metric parts used on multiple engines.) It'* not much of a savings in tooling costs, but it does add up in reduced parts inventory.

You can thank all that "global economy" bs. There'* nothing wrong with the SAE system IMHO.